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211.
In this work, we use Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (13C NMR) data to quantify the changes of major chemical compound classes (carboxylic acid, amide, ester, aliphatic, aromatic and carbohydrate) in high molecular weight (HMW, >1 kDa) dissolved organic matter (DOM) isolated along a transect through the Elizabeth River/Chesapeake Bay system to the coastal Atlantic Ocean off Virginia, USA. Results show that carboxylic acids and aromatic compounds are lost along the transect, while HMW DOC becomes enriched in carbohydrate moieties that could have a mid-transect source, perhaps the intensive red tide bloom (Choclodinium polykrikoides) which occurred during our sampling period. Taking the second derivative of the FTIR spectra resolved three pools of de-protonated carboxylic acids at our Dismal Swamp site (used to represent terrestrial organic matter in this area): one carboxylic acid pool, complexed with iron, seems to be lost between the Dismal Swamp and river sites; the second appears biogeochemically active throughout the riverine transect, disappearing in the coastal ocean sample; the third seems refractory, with the potential to be transported to and to accumulate within the open ocean. Five-member ring esters (γ-lactones) were the major ester form in the Dismal Swamp; aliphatic and acetate esters were the dominant esters in the estuary/marine DOM. No amide groups were detectable in Dismal Swamp DOM; secondary amides were present at the estuarine/marine sites. Coupling FTIR with 13C NMR provides new insights into the biogeochemical roles of carboxylic acid, amide and ester compounds in aquatic ecosystems. 相似文献
212.
Fracture flow modelling based on satellite images of the Wajid Sandstone, Saudi Arabia 总被引:1,自引:0,他引:1
Conny Zeeb Daniel Göckus Paul Bons Hussain Al Ajmi Randolf Rausch Philipp Blum 《Hydrogeology Journal》2010,18(7):1699-1712
Large-scale geological features have been identified by satellite imagery and global positioning system data in the Wajid Sandstone in Saudi Arabia. The main objective is to evaluate the importance of fractures for the overall flow behaviour in this fractured rock aquifer and to estimate in-situ hydraulic apertures. Data on fractures and lineaments were available for three outcrops. By applying a “cut-out” routine on the fracture endpoint data of these fracture trace windows, three deterministic discrete fracture networks (DFN), with an area of 100 m?×?100 m, could be generated. These were used to simulate the fracture flow and to determine the hydraulic conductivity tensors. Using additional data on hydraulic pumping tests and matrix conductivities, in-situ hydraulic apertures could be determined. Average in-situ hydraulic apertures range from 1,300 to 1,700 µm. Observations from the field support these results. In addition, a hydraulic conductivity ratio between the matrix and fracture system was used to identify the contribution of the DFN to the overall fluid transport. A ratio of 10.4 was determined, which indicates that the effective flow behaviour in the Wajid Sandstone aquifer is not entirely dominated by the fracture system, though evidently strongly controlled by it. 相似文献
213.
S.M. Naqvi T. Hanumanth Rao R. Natrajan K. Satyanarayana V. Divakara Rao S.M. Hussain 《Precambrian Research》1977,4(4):361-386
The Chitradurga base metal sulfide deposit is associated with eugeosynclinal metabasalts (~ 2.5 b.y.) and banded pyritiferous cherts. The pre-tectonic character of the deposit and meta-volcanics is indicated by their deformational textures, structures and radioactive age data. The mineral assemblages of these ores are similar to the Zn-Cu type of massive sulfide deposits associated with Archean—Early Precambrian eugeosynclinal metavolcanics in other shield areas. The deposit has a rather high concentration of Co; microprobe data indicate that most of it is found as cobaltite and linnaeite and that it is inhomogenously distributed in these minerals. Very strong sympathetic correlation between Co and Cu, and the simultaneous increase of both of these elements with depth has been found. The geochemistry of the Chitradurga ores and metabasalts, especially their Zn:Cu:Pb and Pb:Zn ratios, suggests that the base metal sulfide content is probably genetically related to the basaltic flows. It appears that the Chitradurga deposit belongs to the ‘massive volcanogenic’ Cu-rich class of sulfide deposits. The metal content of the ores appears to have been supplied by rapidly degassing highly undifferentiated protomantle along with the basaltic magma. 相似文献
214.
Syed Nadeem Hussain Bokhari Thomas C. Meisel 《Geostandards and Geoanalytical Research》2017,41(2):181-195
This work provides a measurement procedure for the complete digestion of rock samples containing refractory minerals such as zircon and chromite. Their dissolution by wet acid digestion is often incomplete but, although providing complete digestions, alkali fusion techniques can result in solutions with a high blank and total dissolved solid content. It was established by the systematic study with reference material trachyandesite MTA‐1 that a 1:6 sample to sodium peroxide (Na2O2) ratio is conservative for the complete digestion and recovery of all the analytes especially those contained in zircon. The sample decomposition time was 120 min for the zircon‐bearing rhyolite reference material MRH‐1. Complete digestion of chromite was obtained in the harzburgite RM MUH‐1. The sample solutions were stable for at least 1 year. Accurate measurements of SiO2, Al2O3, TiO2, P2O5 and K2O could be made with ICP‐MS by not discarding the supernatant of the sinter solution and by using geological reference materials for external calibration. HF digestions are slow, not universal, and may form new mineral/phases that are insoluble under high temperature conditions. The validated sample decomposition procedure combined with ICP‐MS presents an alternative to the use of HF in routine analysis of difficult to digest geological materials. 相似文献
215.
Factors Influencing the Atmospheric Depositional Fluxes of Stable Pb, 210Pb, and 7Be into Chesapeake Bay 总被引:3,自引:0,他引:3
Guebuem Kim N. Hussain J. R. Scudlark T. M. Church 《Journal of Atmospheric Chemistry》2000,36(1):65-79
Atmospheric depositional fluxes of 7Be and210Pb (bulk) and stable Pb (wet) were measuredsimultaneously for one year (from September 1995–August 1996) atStillpond, Maryland on the uppereastern shore of the Chesapeake Bay. The annual total(bulk) depositional fluxes of 210Pb and 7Bewere 0.78 and 13 dpm cm-2, respectively, andagree well with other previously reported results atnearby locations such as Norfolk, VA and Lewes, DE. The wet depositional flux of stable Pb (58 ng cm-2 yr-1)was also similar to thatmeasured at other Chesapeake sites during 1990–1991(55 ng cm-2 yr-1, for both Wye and Elms,Maryland). This suggests that a constant Pb flux hasbeen reached since the mandatory use of unleadedgasoline was instituted. The concentrations of7Be, 210Pb, and to a lesser extent stable Pbwere diluted exponentially by precipitation, based onconcentrations versus precipitation plots. Due tohigher enrichment of 210Pb in the lowertroposphere, the dilution effect was largest on210Pb (i.e., controlled mainly by below-cloudscavenging processes), and thus its depositional fluxincrease is negligible as precipitation amountincreases. A good correlation between the amount ofprecipitation and total depositional flux of 7Beand stable Pb, which are more enriched in the uppertroposphere, suggests that precipitation amount isimportant in controlling their fluxes (i.e.,controlled by both below-cloud scavenging and in-cloudcondensation processes). Based on 7Be versus210Pb plots, it appears that 7Be, relativeto 210Pb, is less efficiently scavenged bysnowfall. Our results suggest that in addition toprecipitation amounts, marine air-mass transport orsnowfall may be important factors in controlling theseasonal variability of the fallout fluxes of tracemetals in coastal areas. 相似文献
216.
S. T. Hussain Ph.D. A. Siddiqa 《International Journal of Environmental Science and Technology》2011,8(2):351-362
Pure titanate nanotubes and titanate nanotubes doped with iron (III) and chromium (III) were fabricated by the hydrothermal treatment in methanol and sodium hydroxide mixture. The fabricated nano tubes have high surface area, high aspect ratio, consisted of very good surface morphology and high metals dispersion. The morphology, crysralline phase, composition were characterized by powdered X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Barrett-Joyner-Halenda methods and X-ray photoelectron spectroscopy. The results showed that nanotubes possess anatase phase and are composed up of 8–12 nm in diameter and 360–400 nm in length. The band gap of the titanium dioxide nanotubes was determined using transformed diffuse reflectance spectroscopy according to the Kubelka-Munk theory, showed pronounced band gap decrease on doped titanium dioxide nanotubes. The photocatalytic activity of doped nanotubes were evaluated in terms of degradation of phenol and photoreduction of carbon dioxide into methanol and ethanol under Ultra violet and Infra red irradiation. It was found that with iron (III) and chromium (III) doped titanium dioxide nanotubes exhibited much higher photocatalytic activity than undoped titanate nanotubes. 相似文献
217.
Nur Hussain S.M. Shahriar Ahmed Amena Muzaffar Shumi 《Singapore journal of tropical geography》2023,44(3):438-458
Urban Heat Island (UHI) refers to a phenomenon whereby urban areas experience higher temperatures compared to the surrounding areas. Remote sensing-based Land Surface Temperature (LST) measurements can be utilized to measure UHI. This study emphasized on geostatistical remote sensing-based hot spot analysis () of UHI in Dhaka, Bangladesh as a way of examining the influences of Land Use Land Cover (LULC) on UHI from 1991 to 2015. Landsat 5 and 7 satellite-based remote sensing indices were used to explore LULC, UHI and environmental footprints during the study period. The Urban Compactness Ratio (CoR) was used to calculate the urban form and augmented characteristics. The Surface Urban Heat Island (SUHI) intensity (ΔT) was also used to explore the effects of UHI on the surrounding marginal area. Based on our investigations into LULC, we discovered that around 71.34 per cent of water bodies and 71.82 percent of vegetation cover decreased from 1991 to 2015 in Dhaka city. Contrastingly, according to CoR readings, 174.13 km2 of urban areas expanded by 249.77 per cent. Our hot spot analysis also revealed that there was a 93.73 per cent increase in hot concentration zones. Furthermore, the average temperature of the study area had increased by 3.26°C. We hope that the methods and results of this study can contribute to further research on urban climate. 相似文献
218.
Al-Qadami Ebrahim Hamid Hussein Mustaffa Zahiraniza Shah Syed Muzzamil Hussain Matínez-Gomariz Eduardo Yusof Khamaruzaman Wan 《Natural Hazards》2022,110(1):325-348
Natural Hazards - Vehicles can be easily swept away by floodwaters once the flow velocity and depth reach certain critical limits, with probabilities toward fatality reported to be nearly 50%.... 相似文献